Swivel chair

ABSTRACT

A swivel chair includes a seat unit and a base unit. The seat unit includes a downwardly extending post. The base unit includes: a base member; a sleeve member that extends upwardly from the base member, that surrounds the post of the seat unit, and that has a top end portion; a bearing that is disposed fixedly in the sleeve member and that is sleeved on the post so as to couple rotatably the post to the sleeve member; a first positioning ring that is fixed in the top end portion of the sleeve member, that surrounds the post, and that forms an annular clearance with the post; and a second positioning ring that is sleeved fixedly on the post, that extends into the first positioning ring, and that is rotatable relative to the first positioning ring.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a chair, more particularly to a swivel chair.

2. Description of the Related Art

Referring to FIGS. 1 and 2, a conventional swivel chair includes a base unit 12 and a seat unit 11, which is pivoted on the top of the base unit 12. The seat unit 11 includes a post 111 pivoted on the base unit 12, and a seat cushion 112 (see FIG. 2) fixed at the upper portion of the post 111. The base unit 12 includes: a base member 121; a sleeve member 122 which surrounds the post 111 and which is fixed to the base member 121; first and second positioning rings 123, 124, which surround the upper and lower portions of the post 111 respectively and which are fixed in the upper and lower end portions of the sleeve member 122 respectively; a third positioning ring 125 that is sleeved fixedly on the post 111, that extends into the first positioning ring 123, and that is rotatable relative to the first positioning ring 123; a fourth positioning ring 126 that is sleeved fixedly on the post 111, that extends into the second positioning ring 124, and that is rotatable relative to the second positioning ring 124; and a bolt assembly 127 which is disposed inside the fourth positioning ring 126 and which engages one end of the post 111 to position the post 111 inside the sleeve member 122.

In the design of the conventional swivel chair, the requisite rotation of the seat unit 11 relative to the base unit 12 is achieved as a result of the rotation of the post 111 and the third and fourth positioning rings 125, 126 relative to the first and second positioning rings 123, 124. However, since the components of the base unit 12 are numerous, manufacture of the conventional swivel chair is excessively complicated. In addition, the friction between the positioning rings 123-126 has an adverse affect on smooth rotation of the seat unit 11.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a swivel chair that is capable of overcoming the aforementioned drawbacks of the prior art.

According to the present invention, there is provided a swivel chair that comprises a seat unit and a base unit. The seat unit includes a downwardly extending post. The base unit includes a base member, a sleeve member, a bearing, and first and second positioning rings. The sleeve member extends upwardly from the base member, surrounds the post of the seat unit, and has a top end portion. The bearing is disposed fixedly in the sleeve member, and is sleeved on the post so as to couple rotatably the post to the sleeve member. The first positioning ring is fixed in the top end portion of the sleeve member, surrounds the post, and forms an annular clearance with the post. The second positioning ring is sleeved fixedly on the post, extends into the first positioning ring, and is rotatable relative to the first positioning ring.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:

FIG. 1 is an exploded perspective view of a conventional swivel chair;

FIG. 2 is a partly sectional, schematic side view of the conventional swivel chair;

FIG. 3 is an exploded perspective view of the preferred embodiment of a swivel chair according to this invention; and

FIG. 4 is a partly sectional, schematic side view of the swivel chair of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 3 and 4 illustrate a preferred embodiment of a swivel chair according to this invention. The swivel chair comprises a seat unit 4 and a base unit 3. The seat unit 4 includes a downwardly extending post 42, and a seat cushion 41 fixed to a top end of the post 42. The base unit 3 includes: a base member 31; a sleeve member 32 that extends upwardly from the base member 31, that surrounds the post 42 of the seat unit 4, and that has a top end portion; a bearing 33 that is disposed fixedly in the sleeve member 32 and that is sleeved on the post 42 so as to couple rotatably the post 42 to the sleeve member 32; a first positioning ring 34 that is fixed in the top end portion of the sleeve member 32, that surrounds the post 42, and that forms an annular clearance with the post 42; and a second positioning ring 35 that is sleeved fixedly on the post 42, that extends into the first positioning ring 34, and that is rotatable relative to the first positioning ring 34. Since the bearing 33 is a conventional component, details of the same are omitted herein for the sake of brevity.

Preferably, the first positioning ring 34 includes a lower ring segment 341 that surrounds the post 42 and that forms the annular clearance with the post 42, and an upper ring segment 342 that extends coaxially and upwardly from the lower ring segment 341. The upper ring segment 342 has an inner ring surface that defines a ring space gradually diverging in an upward direction, and the second positioning ring 35 has an outer diameter that is gradually reduced in a downward direction. The second positioning ring 35 is received rotatably in the ring space of the upper ring segment 342 of the first positioning ring 34. The first and second positioning rings 34, 35 ensure that the post 42 cannot tilt within the sleeve member 32.

Preferably, the post 42 is hollow and has a bottom end portion that abuts against the base member 31, and the seat unit 4 further includes a nut 43 fixed in the bottom end portion of the post 42. The base unit 3 further includes a bolt 36 that passes through the base member 31 and that threadedly engages the nut 43, thereby retaining rotatably the post 42 on the base member 31. Alternatively, the nut 43 could be fixed directly to the bottom of the post 42 such that the nut 43 is disposed between the post 43 and the base member 31. In yet another alternative, the post 42 is solid and the nut 43 is omitted. In this case, the bottom end portion of the post 42 is formed with a borehole (not shown) so that the bolt 36 could threadedly and directly engage the post 42. The rotatable retention of the post 42 on the base unit 3 is not limited to the above suggestions.

It has thus been shown that the base unit 3 of the swivel chair of this invention requires fewer components to retain the seat unit 4 rotatably on the base unit 3 when compared to the conventional swivel chair of FIG. 1. Moreover, with the inclusion of the bearing 33 between the post 42 and the sleeve member 32, smooth rotation of the seat unit 4 relative to the base unit 3 can be ensured.

While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

1. A swivel chair, comprising: a seat unit including a downwardly extending post; and a base unit including a base member, a sleeve member that extends upwardly from said base member, that surrounds said post of said seat unit, and that has a top end portion, a bearing that is disposed fixedly in said sleeve member and that is sleeved on said post so as to couple rotatably said post to said sleeve member, a first positioning ring that is fixed in said top end portion of said sleeve member, that surrounds said post, and that forms an annular clearance with said post, and a second positioning ring that is sleeved fixedly on said post, that extends into said first positioning ring, and that is rotatable relative to said first positioning ring.
 2. The swivel chair as claimed in claim 1, wherein: said first positioning ring includes a lower ring segment that surrounds said post and that forms said annular clearance with said post, and an upper ring segment that extends coaxially and upwardly from said lower ring segment, said upper ring segment having an inner ring surface that defines a ring space gradually diverging in an upward direction, and said second positioning ring has an outer diameter that is gradually reduced in a downward direction, and is received rotatably in said ring space of said upper ring segment of said first positioning ring.
 3. The swivel chair as claimed in claim 1, wherein: said post has a bottom end portion, and said seat unit further includes a nut fixed to said bottom end portion of said post, and said base unit further includes a bolt that passes through said base member and that threadedly engages said nut, thereby retaining rotatably said post on said base member.
 4. The swivel chair as claimed in claim 1, wherein said base unit further includes a bolt that passes through said base member and that threadedly engages said post, thereby retaining rotatably said post on said base member. 